Production of spinnable vinyl resin compositions



Patented Apr- 8 1947 ENT OFFICE PRODUCTION SPINNABLE VINYL COMPOSITIONSRoland 1). Glenn. South Charleston, w. ya, u-

sig-nor to Carbide and Carbon Ohemlcak poration, a corporation of NewYork Application August 16, 1944, Serial No. 549,798

No Drawing.

Cor-

'2 Claims. (01260-42) l This invention relates to the production ofsplnnable vinyl resin compositions capable of be ing formed intocontinuous filaments. threads; yarns and the like by commerciallypracticable spinning operations; It has especial utility for theproduction of continuous filaments and threads from dispersions inacetone or other volatile solvent of vinyl resins having relatively highvinyl chloride contents and high average molecular weights, such asthose formed by the so-called emulsion polymerization of at least onevinyl compound including a vinyl halide. These resin dispersions oftenare not spinnable or are difilcultly spinnable by the usual spinningoperations.

Vinyl resins made by the copolymerization of a vinyl halide with anotherunsaturated polymerizable compound, such as a vinyl ester of analiphatic acid, or an acrylic compound such as acrylonitrileor theacrylic acid esters, or the methacrylic acid esters, have long beenknown. The manufacture of filaments and other textile articles fromcertain copolymers of vinyl chloride and vinyl acetate is described inUnited States Patent No. 2,161,766 of E. W. Rugeley. T. A. Feild, Jr.,and J. F. Conlon. Likewise, the production of spinning solutions,filaments and other textile articles from certain vinylhalide-acrylonitrile copolymers is described in the pending application,

Serial No. 476,616, of E. W. Rugeley, T. A. Feild,

Jr.; and J. L. Petrokubi, filed February 20, 1943.

In instances when the resin employed has been produced by polymerizingthe vinyl compounds in solution in acetone or other volatile solventuntil the resin possesses the requisite high molecular weight, specificviscosity and vinyl chloride content, it is readily possible to prepareconcentrated dispersions of the resin in a spinnin solvent such asacetone, which are readily filterable and spinnable, at temperaturesaround 50 C., in accordance with the usual practice.

In recent years processes have been developed for producing these vinylresins by the so-called emulsion polmerization type of process whereina, vinyl halide, with or without the addition of another polymerizablevinyl compound, 'in the form of an aqueous emulsion containing apolymerization catalyst, is polymerized to produce vinyl resins havingproperties rendering them suitable for use in making spinnabledispersions in volatile solvents, notably acetone. Processes of thistype are described in United States Patent No. 2,068,424, and in theaforementioned pending application, Serial No. 476,616.

Efforts are constantly being made to improve the physical properties ofyarns made from such by utilizing resins or higher average molecularweights and higher vinylchloride contents. The production or such resinsis more 9 readily accomplished by emulsion polymerization Zolocesses. Itis not necessary to fractionate these resins for removal of the lowermolecular weight portions. However, during the production of the highermolecular weight resins by emulsion polymerization processes the resinsmay reach a. critical state where they possess inadequate solubility inacetone' or other spinning solvent to render dispersions thereofpractically spinnable by the established dry-spinning and wet-spinningproceclures. i

As a result, the task oi making smooth, gel-free spinnable dispersionsof these vinyl resins which,

do not clog the candle filters and cause excessively high back pressuresin filters and spinnerette passages often is very great, and diflersconsiderably without any apparent reason, in dispersions made undersimilar conditions. f

Among the more important objects of the present invention are: thepreparation of uniform spinnable vinyl resin dispersions adapted for thecontinuous production of filaments, yarns. etc, from vinyl resins madeby the emulsion type of polymerization of at least one polymerizablevinyl compound including a vinyl halide the production of concentratedspinnable dispersions of vinyl resins having vinyl chloride contentsand/or average molecular weights and specific viscosities too high torender such dispersions spinnable by the usual procedures heretoforeused; o provide spinnable dispersions of vinyl resins which normallyform with volatile spinning solvents dispersions containing smallquantities of resins difflcultly soluble or dispersible in the solventat the'spinning temperatures; and to provide for the production ofexceptionally clear dispersions of excellent spinnability from a gradeof vinyl resin not heretofore found useful for the purpose,

'withoutlowering the tensile strengths and other desired physicalproperties of the filaments spun therefrom.

Vinyl resins, dispersions of which are not readily spinnable but whichare rendered capable of producing excellent spinnable dispersions as aresult of treatment in accordance with this invention include those madeby the conjoint emulsion polymerization of a vinyl halide and a vinylester of an aliphatic acid, which resins contain between about and aboutofthe halide in the polymer, and have average macromolecular weightscommonly of 25,000 and upward. Resins of this type having averagemacromolecular weights above 25,000. and particularly between 26,000 and29,000, and/or having vinyl chloride contents. of around 90% to 92%, areespecially benefitted by the invention,'and are rendered suitable forthe spinning of filaments and yarn by conventional procedures.(Molecular weights mentioned herein are calculated by means ofStaudingers .formula from viscosity measurements of solutions oftheresins.) Other suitable resins benefitted by the invention include thosemade by the emulsion polymerization of a vinyl halide withacrylonitrile, which resins contain between around 45% and around 80% ofthe halide in the polymer, and have specific vi'scosities at 20 C. of atleast around 0.2, and especially those resins having vinyl chloridecontents of around 55% or more and specific viscosities of 0.35 or her.i or convenience and simplicity the invention will be illustrated inconnection with the preparation of spinnable dispersions ,in acetone ofvinyl resins produced by the conjoint polymerization of vinyl halideswith vinyl esters of aliphatic acids. and with acrylonitrile.

A typical process for the production of spin able dispersions from vinylresins made by polymerizing at least one vinyl compound including avinyl halide is described in the aforesaid United States Patent No.2,161,766. It comprises the dispersion of the resin in a volatilespinning solvent such as acetone by working or kneading the resin andacetone in a closed dough-type mixer while at a'temperature below theboiling pointof the acetone, and preferably around 50 C.

Any vaporized acetone is refluxed and returned to the mixer. Theresultant spinning dope, when intended for use in a dry-spinning type ofoperation,.is a very viscous slowly fiowable mass at 50 C. (Dopes"useful for wet-spinning are more dilute and less viscous.) This viscousdis.- persion is then forced through a high-pressure filter press by agear pump. The filter medium may-be any suitable material capable ofremoving the last traces of undispersed or insoluble.material from thedope." The filtered dope is thoroughly deaerated, preferably by standingfor about six hours at the spinning temperature of around 50 C. It isthen forced under high ressure through a spinnerette of well-known type,the spinning operation or filament extrusion being carried out either inequipment customarily employed for the so-called dry-spinning or in thatused for the wet-spinning of synthetic filaments.

This manner of preparation frequently yields dispersions which containresin gel particles and which are not spinnable by the usual processes,especially when the resins have the higher average molecular weights ofthose produced by wellknown emulsion polymerization procedures.

In the practice of the present invention, such a resin dispersion, whichis not readily spinnable by the usual wetand dry-spinning processes, isheated to an elevated temperature within the range between around 80 C.and around 100 C. at some stage or stagesin its preparation, or itssubsequent filtration or storage, and while under superatmosphericpressure suflicient to prevent loss of acetone or other solvent. Theheating time may range from as little asiive minutes upwardly, dependingupon the temperature to which the resin dispersion is thus heated. Theupper temperature limit is dictated by the decomposition point of theresin and by the pres-' sure equipment availablefor the operation. For

practical reasons temperatures within the range between 80 C. and 100 C.preferably are employed for periods usually ranging between 5 minutesand 1 hour, thehigher temperatures usually being employed with theshorter periods of exposure at such temperatures. Preferably thedispersion is maintained in anatmosphere of an inert gas such asnitrogen or carbon dioxide duringthe heat treatment under a pressure inexcess of the vapor pressure of the solvent at the e temperature of thetreatment.

The vinyl resin dispersion may be heat treated either batchwise orcontinuously, and before, during or even after the high temperaturefiltration. When a continuous type of heat treatment is employed it isgenerally applied at a heated filter press in connection with the highpressure, high temperature filtration of the dispersion, since thisprovides adequate time for the treatment, excellent contact of the resindispersion with the heat transfer elements of the filter, and goodagitation of the dispersion during the heat treatment. a According toone preferred form 01' the invention a vinyl resin of the type hereindescribed may be dissolved in acetone at temperatures within the rangebetween 40 C. and 60 C. in a closed high pressure, jacketed-typekneading mixer. In instances where temperatures below the normal boilingpoint of the solvent'are used in the initial preparation of the resindispersion, the latter, after its formation, may be heated withagitation for a period of from 5 minutes to 1 hour or more to atemperature within the range between around 80 C. and around 100 C. in ajacketed autoclave or other pressure-tight apparatus, while under asuperatmospheric pressure sufiicient to prevent loss of the acetone orother solvent. Preferably during this heating step the resin dispersionis maintained in an atmosphere of an inert gas such as nitrogen orcarbon dioxide. This assists in preventing the formation of a skin ofhardened resin on the walls of the autoclave, apparently caused by thelocal evaporation of acetone from a. stagnant layer of the resindispersion adjacent the hot walls. The dispersion is then filtered at atemperature between 55 C. and 100 C., cooled, if necessary, to about 55C., and spun in the conventional manner.

In accordance with another preferred form of the invention wherein theheat treatment is conducted in a continuous manner, the dispersion ofthe vinyl resin, produced by kneading the mixture of resin and acetoneat a temperature below the boiling point of the acetone, for example,

around 50 C., is forced through a heated presa brief period .of not lessthan 5 minutes, and

preferably for from 10 to 30 minutes or more. The heated solution, afterbeing cooled to around 30 C. to 55 C., may be fed directly to the candlefilter in the spinning cell. Preferably the heat treated resindispersion -flows from the pressure filter to a pressure storage andaging vessel where gradual cooling occurs, and from whic a p rtion iscontinuously withdrawn and conducted to th spinning cell as required. i

For practical reasons it is desirable, when using acetone as the solventto agitate the resin and acetone in a pressure-tight kneading type ofmixer, while heating it to a temperature not higher than around 50 C. to55 C. until dispersion of the resin has been effected, after which thedispersion is heated under pressure to a temperature of between around80 C. and around 90 C. for about one hour. The hot dispersion is thenfiltered while at a temperature within the range between around 55 C.and around 90 C. The filtered dispersion is cooled to around 50 C. to 55C., and may then be stored at such temperatures until required, or itmay be directly forced through a candle filter and spun in the usualmanner described in United States Patent No. 2,161,766, and in theaforesaid pending application. Serial No. 476,616.

The heat-treated resin dispersions of the invention have somewhat lowerviscosities than untreated resin dispersions of the same concentration,measured at the same temperature. It is advantageous therefore to spindispersions having higher resin contents than heretofore has been foundpractical. Dispersions useful for dry spinning operations mayconveniently have resin'concentrations of 20% to 35% or more; whilethose useful in wet-spinning operations may have resin concentrationsaround 12% to 18% or,mo re.

The following examples serve to illustrate the invention:

Example I A vinyl resin formed by the conjoint polymerization of vinylchloride and vinyl acetate by an emulsion polymerization process, whichresin contained 91.1% of vinyl chloride in the polymer and had aspecific viscosity at 20 C. of 0.307, and an average macromolecularweight of 26,800, was mixed with acetone in a Day type kneading mixer attemperatures between 40 C. and 55 C. to yield a resin dispersioncontaining 20% of the resin. The dispersion was hazy and contained resingels which caused filtration difilculties, Serious back pressuredeveloped during attempts to spin this resin solution by the dryspinning process employing standard equipment.

A quantity of this resin was dissolved in acetone in a kneading typemixer to form a more concentrated extremely viscous dispersioncontaining31% ed to 90 C. for 1 hour in .an atmosphere of nitrogen in aheat-jacketed glass-lined autoclave having an agitator and maintained.under a nitrogen pressure of 45 pounds per square inch, gauge. Afterdiluting the heat-treated dispersion to a resin content of 27%,itwasfiltered-through a pressure filter while at 85C., and was then cooled toaround 50 C. This heat treated resin dispersion was of excellent clarityand possessed about the same viscosity as that of a 20% concentrateddispersion of the resin mixed at 50C. only. The former exhibitedexcellent spinn'ability; andno excessive back pressure developed duringthe spinning thereof. The spun fibers, after being stretched 463% at 125C. in asteani cell, had tenacities of 3.5 grams per denier, and hadelonations of 18.8%.

' Example]! AIquantity of a vinyl chloride-vinyl acetate copolymer resincontaining 90.8% of the chloride in the polymer and havinga specificviscosity at 20 C. of 0.319 and an average macromolecular weight of25,600. was mixed at around-50 C. in a closed kneading ,mixer with.sufiicient acetone to yield a dispersion containing 25% of the resin.

of the resin. The dispersion was then heatfilaments of good Thedispersion was then heated, with agitation. for one hour at 85 C. in anatmosphere of nitrogen, in a pressure-tight kneading mixer, while undera pressure of 49 pounds per square inch, gauge.

The resultant colorless spinning dispersion was filtered through apressure filter while at 85 C.

' The filtered dispersion was then cooled to around 50 C., passedthrough a candle filter, and spun, using a dry-spinning procedure of thegeneral type described in United States Patent No. 2,161,766.

The treated resin dispersion had excellent spinning 'qualities; and noexcessive back pressure developed during spinning thereof. The spunfilaments, when processed in the general manner described in Example I,had tenacitlesof 3.6 grams per denier, and elongations of 22%.

In contrast with these results, a 19.5% dispersion of the same resin inacetone, which dispersion was not given the heat treatment of thisinvention. had very poor spinning characteristics. During the course ofthe spinning operation an excessive back pressure of 420 pounds persquare inch'developed, over and above the pressure normally used,although the concentration of the Example III A vinyl resin of the typedescribed in Example 11 was dispersed at atmospheric pressure inapproximately three times its weight of acetone in a closed dough-typemixer operating at a temperature of around-55 C. The resultantdispersionwas pumped by a gear pump through a filter press in which alternateplates were internally heated to about 80 C. by means of hot water. Thefiltration of 1600 pounds of this dispersion through a heated 24-inchfilter, press having 24 plates required 4 hours. The filtered dispersionwas then forced into a storage vessel maintained under a pressure ofabout 25 pounds per square inch gauge. The temperature of the dispersiongradually fell during storage so that. as it was pumped to the spinningapparatus, its temperature was around 40 C. to 45 C.

The heat treated dispersion was readily spinnable by a dry-spinningoperation to provide quality.

Example IV R A quantity of vinyl chloride-acrylonitrile co polymer resincontaining around 60% of the.

chloride in the polymer andhaving a specific viscosity at 20 C. of .350,and produced by an emulsion polymerization process of the type describedin 'theaforesaid pending application,

Serial No. 476,616, was mixed with acetone in a.

closedkneading type mixer to yield a resin persion containing 19.5% ofthe resin.

The dispersion was somewhat hazy and slowly flowable. at temperaturesaround 50 C; Its spinning propertieswere not satisfactory due to theexcessive, constantly increasingback pressure in the spinning candlespinning operation.

The aforesaid dispersion was then filteredunder pressure through twojacketed type candle filters arranged-in series. The first filter washeated to around C. by hot water in the jacket thereof; and the resindispersion was filtered at such a rate that it was exposed to this hightemperature filter system during the 7 for approximately minutes. Theheated dispersion then was passed through the second filter which wascooled by means of water at room temperatures in the jacket thereof, toprevent or minimize loss .of solvent from the dispersion upon thesubsequent release of pressure.

- The heat treated dispersion was transferred to after being stretched1289% at 132 C., and the stretched yarn stabilized by immersion in anuntensioned state for 1 hour in Water at 100 0., had a wet tenacity of4.5 grams per denier, and an elongation of 26.5%. The yarn wasofexcellent quality; and the filaments thereof were of uniform size.

The vinyl resins used in the preparation of spinning dispersions inaccordance with the invention preferably contain small amounts of heat'ever, a wide variety of other well-known heat stabilizers for vinylresins may be utilized, in amounts ranging upward from 0.1% of theresin.

By the practice of this invention it is possible to spin vinyl resindispersions which, while formed from resins having excellent physicalproperties per se, are not commercially spinnable by standard spinningtechniques because of the resins having unduly high vinyl chloridecontents and/or average molecular weight, and because of beingcontaminated with small quantities of resins that are difiicultlysoluble in the spinning solvent due to insufiicient control over thepolymerization and resin recovery processes. Dispersions having higherresin concentrations may be successfully spun. This results in 'aneconomy of solvent and facilitates the treatment of the spun filamentsand yarns for removal of the solvent.

The invention is susceptible ofmodification within the scope'of theappended claims.

I claim:

1. Process for preparing a spinnable dispersion in a volatile spinningsolvent of a vinyl resin formed by the emulsion polymerization of notmore than two vinyl compounds including a vinyl halide, said resincontaining components incomthe resin dispersion for a period of at leastfive minutes to a temperature within the range between around 80 C. andaround 100 C. but above the boiling point of the solvent at atmosphericpressure while under superatmospheric pressure sufiicient to minimizelocal evaporation of the solvent, thereby providing a. spinnabledispersion of greatly improved spinning characteristics.

2. Process Ior preparing a spinnable dispersion in a volatile solvent ofa vinyl resin of high average molecular weight formed by the emulsionpolymerization of not more than two vinyl compounds including a vinylhalide, which resin contains components incompletely dispersible in thesolvent at the spinning temperature, thereby inhibiting the spinning ofthe resin dispersion in said solvent, which comprises intimately mixingsuch a vinyl resin with a body of said solvent to form a resindispersion, filtering such dispersion under high pressure at an elevatedtern-- perature of at least 50 C., and conducting the filtereddispersion to a spinning operation while at a temperature within therange from 30 C. to about 55 C., and, at some stage in the process,heating the resin'dispersion under pressure, for a period of from atleast five minutes to an hour, to a temperature within the range betweenaround 80 C. and around 100 C. but above the boiling point of the saidsolvent at atmospheric pressure, while preventing loss of solvent from'saiddispersion, thereby providing a spinnable dispersion of greatlyimproved spinning characteristics.

3. Process as defined in claim 2 wherein the solvent is acetone.

4. Process for preparing a spinnable dispersion in a volatile solventofa vinyl resin formed by .the emulsion polymerization of not more thantwo vinyl compounds including a vinyl halide, which resin containscomponents normally incomplete the presence of an inert gas, whilepreventing loss of solvent, filtering the resultant heat treateddispersion under high pressure while at a' temperature within the rangebetween around 55 C. and around 100 C., and conducting the thus heattreated and filtered. resin dispersion to a spinning zone while at atemperature of between about 30 C. and about 55 0., thereby providing aspinnable dispersion of greatly improved spinning characteristics.

5. Process. for preparing a spinnable dispersion in a volatile spinningsolvent of a vinyl resin minutes and one hour at, a temperature withinducting it to a spinning zone while at a temperature of between about 30C. and about 55 C., thereby providing at the spinning zone a spinnabledispersion having greatly improved spinning characteristics.

6. Process for preparing a spinnable disper--,

sion in acetone of a vinyl resin formed by the conjoint emulsionpolymerization of a vinyl halide with a vinyl ester of an aliphaticacid, which resin contains between about 80% and about 95% of the halidein the polymer and has an average macromolecular weight of at least25,000, said resin containing components normally not completelydispersible in acetone at the spinning temperature, thereby interferingwith the spinnability of a dispersion thereof in acetone by conventionalwetand dry-spinning procedures,which comprises intimately mixing such avinyl resin with acetone at an elevated temperature to form a resindispersion, filtering such dispersion under pressure, and conducting theresultant filtered dispersion to a spinning operation while at atemperature within the range between about 30 C, and about 55 C., and,atsome stage in the process prior to said spinning operation, heatingthe resin dispersion for a period of at least five minutes to atemperature within the range between around 80 C. and around 100 C.while under superatmospheric pressure sufficient to minimize localevaporation of th acetone, there- 10 by providing a spinnable dispersionof greatly improved spinning characteristics.

'7. Process for preparing a spinnable dispersion in acetone of a vinylresin formed by the conjoint emulsion polymerization of a vinyl halidewith acrylonitrile, which resin contains between around and around 80%of the halide in the polymer and has a specific viscosity at 20 C. of atleast around 0.2, said resin containing components rendering adispersion thereof in acetone difliculty spinnable by conventionalwetand dryspinning procedures, which comprises intimately mixing such avinyl resin with acetone at an elevated temperature to form a resindispersion,

filtering such dispersion under pressure, and conducting the resultantiiltered dispersion to a spinning operation while at a temperaturewithin the range between about 30 C. and about C., and, at some stage inthe process, prior to said spinning operation, heating the resin dis-REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED) STATES PATENTS Name Date Rugeley et al. June 6, 1939 Number

